Water soluble insulating varnish

Claim 1

A polyester comprising an oil-free and fatty-acid reaction product of component A and component B wherein component A is the reaction product of at least one aromatic dicarboxylic acid selected from the group consisting of isophthalic acid, terephthalic acid, benzophenone dicarboxylic acid and mixtures thereof, wherein the aromatic dicarboxylic acid is used in an amount ranging from 35 to 85 mole percent based on the combined amounts of the aromatic dicarboxylic acid and component B; and of at least one polyhydric alcohol selected from the group consisting of neopentyl glycol, 1,4-butylene glycol, dimethylol hydantoin, dipropylene glycol, ethylene glycol, diethylene glycol, propylene glycol, cyclohexane dimethanol, hydrogenated bisphenol A, hydroquinone di-(beta-hydroxyethyl) ether, ethylene glycol diether of bisphenol A, and propylene glycol diether of bisphenol A; and wherein component B is trimellitic anhydride or trimellitic anhydride admixed with material selected from the group consisting of tetrahydrophthalic acid, hexahydrophthalic acid, 3,6-endomethylene-delta 4 -tetrahydrophthalic acid, adipic acid, succinic acid, azelaic acid, sebacic acid, dimerized fatty acid, maleic acid, fumaric acid, anhydrides of said acids and mixtures thereof, component B being used in an amount of 15-65 mole percent of the combined amount of aromatic dicarboxylic acid and component B; wherein the OH/COOH ratio of the polyester is from 1:1 to 1.5:1; wherein since B is trimellitic anhydride or a mixture containing trimellitic anhydride, the polyhydric alcohol consists essentially of a diol or mixture of diols; wherein the polyester has an acid number of from 25 to 90 measured on a sample diluted to 80% solids.